The present invention pertains generally to acoustics and more specifically to underwater control systems.
In the sub-surface mooring of ordnance devices, such as mines, torpedo, and the like, it is desirable to control the functioning of these devices from the surface. Prior systems for underwater control have included cable linked control systems, preset timer activated control systems, and conventional acoustic control systems.
The disadvantage of the cable-linked control systems is that they require physical cables from the sub-surface mooring to a support vessel. This type of device is vulnerable to cable damage by both storms and ship motion. Also, the cost of keeping a ship on station for long periods of time would be prohibitive.
The disadvantage of the preset timer-activated control systems is a lack of flexibility in activating the device. For instance, this system might be preset to release a sub-surface mooring after one month. If the weather happens to be too stormy for a vessel to attempt the recovery, the mooring would probably be lost.
The conventional acoustic control systems that have been in use for the last several years have demonstrated reliable operation and have proved their usefulness for many undersea control tasks. These conventional acoustic control systems however are typically packaged in sizable pressure housings which may vary in weight from 40 to 130 pounds in air. These pressure housings are usually attached to, or form an integral part of, the anchor cable of the sub-surface mooring. The bulk of these older acoustic control systems and their attachment location place limitations on their use. These limitations are particularly apparent when the acoustic control system is to be used for the testing of underwater ordnance. The fact that most sub-surface moored ordnance are either dropped from an aircraft or launched from a submarine's torpedo tube precludes the attachment of a separate pressure housing. In addition, it is impossible to attach the acoustic control housing between the anchor and the ordnance device to be moored since the ordnance device, cable, and anchor are typically launched as a single package. Further, the conventional acoustic control systems fail to use coding methods so that unauthorized signal are often interpreted as control input signals.